Condenser refrigerant distribution

ABSTRACT

A flow regulator being disposed in at least one of the outlets of a condenser to regulate the fluid flow in the condenser. The condenser has at least two fluid flow paths and an air flow drawn through the condenser by a condenser fan. The flow regulator regulates the fluid flow to substantially equalize the temperature of the fluid flow in the at least two fluid paths and to provide more efficient cooling of the fluid in the fluid flow paths.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Nos. 60/882,033 filed on Dec. 27, 2006; 60/914,489 filed onApr. 27, 2007 and 60/952,280 and filed on Jul. 27, 2007, all of whichrelate to multichannel technology and are hereby incorporated byreference in their entirety into this application.

BACKGROUND

The application generally relates to multichannel heat exchangerapplications in HVAC&R systems. The application relates morespecifically to improved refrigerant distribution in a condenser thatuses multichannel heat exchangers.

In a typical multichannel heat exchanger or coil slab, a series of tubesections are connected (physically and thermally) by fins that areconfigured to permit airflow through the heat exchanger in order toprovide for heat transfer between the airflow and a circulating fluid,e.g., water or refrigerant. The tube sections of the heat exchanger areoriented to extend either horizontally or vertically and each tubesection has several tubes or channels that are used to circulate thefluid. The outside of the tube section is a continuous surface typicallyhaving a rectangular shape.

Multichannel heat exchangers can offer significant cost and performanceadvantages when used in an air-cooled condenser of a HVAC&R systemcompared to conventional round-tube condenser coils. One performanceadvantage offered by a multichannel heat exchanger is a reduced airpressure drop through the condenser compared to a conventionalround-tube coil. The multichannel heat exchanger can be designed so thata single heat exchanger or row performs the de-superheating andsub-cooling process in the condenser based on the number of passes inthe heat exchanger. In a two-pass design, the two phase refrigerantexiting the first pass is mixed in an intermediate header beforeentering the second pass where condensation is completed and sub-coolingis done. Further, a multichannel heat exchanger may be constructed ofaluminum, which can reduce material cost and enhance performance in arefrigeration system. The reduced air pressure drop in a multichannelheat exchanger forces and uneven air distribution between the coils.This uneven air distribution in multichannel coils results in largevariations in refrigerant liquid temperature. Therefore, what is neededis a system and method for more evenly distributing the refrigerant flowin multichannel coils, thereby improving the distribution of refrigerantliquid temperature as well.

Intended advantages of a system and/or method satisfy one or more ofthese needs or provide other advantageous features. Other features andadvantages will be made apparent from the present specification. Theteachings disclosed extend to those embodiments that fall within thescope of the claims, regardless of whether they accomplish one or moreof the aforementioned needs.

SUMMARY

One embodiment is directed to an HVAC&R system having a compressor, acondenser, an evaporator, and an expansion valve connected in a closedrefrigerant loop. The condenser has at least two fluid flow paths thatare cooled by an air flow drawn through the condenser by at least onecondenser fan. The at least two fluid flow paths each have an inlet andan outlet and a fluid flow between the inlet and the outlet. The atleast two fluid flow paths have a variable air flow for cooling thefluid in the at least two fluid flow paths. At least one flow regulatoris disposed in at least one outlet to regulate at least one fluid flowin response to the variable air flow in the condenser. The flowregulator regulates the fluid flow in the at least two flow paths toprovide a fluid having a substantially equal temperature in the at leasttwo flow paths.

Another embodiment is directed to a condenser has at least two fluidflow paths that are cooled by an air flow drawn or directed through thecondenser by at least one condenser fan. The at least two fluid flowpaths each have an inlet and an outlet and a fluid flow between theinlet and the outlet. The at least two fluid flow paths have a variableair flow for cooling the fluid flow in the at least two fluid flowpaths. At least one flow regulator is disposed in at least one outlet toregulate at least one fluid flow in response to the variable air flow inthe condenser. The flow regulator regulates the fluid flow in the atleast two flow paths to provide a fluid having a substantially equaltemperature in the at least two flow paths.

Yet another embodiment is directed to a condenser, which has amultichannel heat exchanger. The multichannel heat exchanger has atleast two fluid flow paths that are cooled by an air flow drawn orotherwise directed through the condenser by at least one condenser fan.The at least two fluid flow paths each have an inlet and an outlet and afluid flow between the inlet and the outlet. The at least two fluid flowpaths have a variable air flow for cooling the fluid in the at least twofluid flow paths. At least one flow regulator is disposed in at leastone outlet to regulate at least one fluid flow in response to thevariable air flow in the condenser. The flow regulator regulates thefluid flow in the at least two flow paths to provide a fluid having asubstantially equal temperature in the at least two flow paths.

One advantage is improved liquid subcooling temperatures of therefrigerant to assure reliable performance of the expansion valve.

Another advantage is improved protection against equipment performancedegradation.

Yet another advantage is increased chiller cooling capacity.

Still another advantage is a reduced cost system and increased systemefficiency, when compared to conventional systems.

Alternative exemplary embodiments relate to other features andcombinations of features as may be generally recited in the claims.

BRIEF DESCRIPTION OF THE FIGURES

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is an illustration of an exemplary residential air conditioningor heat pump system of the type that might employ a heat exchanger madeor configured in accordance with the present techniques;

FIG. 2 is a partially exploded view of the outside unit of the system ofFIG. 1, with an upper assembly lifted to expose certain of the systemcomponents, including a heat exchanger;

FIG. 3 is an illustration of an exemplary commercial or industrialHVAC&R system that employs a chiller and air handlers to cool a buildingand that may also employ heat exchangers in accordance with the presenttechniques;

FIG. 4 is a partially exploded view of the exemplary commercial orindustrial HVAC&R system that employs a chiller and air handlers to coola building of FIG. 3, with the fan assembly lifted to expose certainsystem components, including a heat exchanger;

FIG. 5 is a diagrammatical overview of an exemplary air conditioningsystem which may employ one or more heat exchangers with internal tubeconfigurations in accordance with aspects of the invention;

FIG. 6 is a diagrammatical overview of an exemplary heat pump systemwhich may employ one or more heat exchangers with internal tubeconfigurations in accordance with aspects of the invention;

FIG. 7 is a perspective view of an exemplary heat exchanger containinginternal tube configurations in accordance with one aspect of theinvention;

FIG. 8 is a partially exploded detail perspective view of an exemplarymultichannel tube;

FIG. 9 is an end view of a condenser of FIG. 3;

FIG. 10 is an enlarged view of the outlet with an orifice;

Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or like parts.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Turning now to the drawings, and referring first to FIGS. 1-3, exemplaryapplications for aspects of the invention are illustrated. Theinvention, in general, may be applied in a wide range of settings, bothwithin the HVAC&R field and outside of that field. In presentlycontemplated applications, however, the invention may be used inresidential, commercial, light industrial, industrial and in any otherapplication for heating or cooling a volume or enclosure, such as aresidence, building, structure, and so forth. Moreover, the inventionmay be used in industrial applications, where appropriate, for basicrefrigeration and heating of various fluids. The particular applicationillustrated in FIG. 1 is for residential heating and cooling. Ingeneral, a residence, designated by the letter R, will be equipped withan outdoor unit that is operatively coupled to an indoor unit. Theoutdoor unit is typically situated adjacent to a side of the residenceand is covered by a shroud to protect the system components and toprevent leaves and other contaminants from entering the unit. The indoorunit may be positioned in a utility room, an attic, a basement, and soforth. The outdoor unit is coupled to the indoor unit by refrigerantconduits RC, which transfer primarily liquid refrigerant in onedirection and primarily vaporized refrigerant in an opposite direction.

In operation, when the system shown in FIG. 1 is operating as an airconditioner, a coil in the outdoor unit serves as a condenser forrecondensing vaporized refrigerant flowing from the indoor unit IU tothe outdoor unit OU via one of the refrigerant conduits. In theseapplications, a coil of the indoor unit, designated by the referencecharacters IC, serves as an evaporator coil. The evaporator coilreceives liquid refrigerant (which may be expanded by an expansiondevice described below) and evaporates the refrigerant before returningit to the outdoor unit.

In operation, the outdoor unit draws in environmental air through sidesas indicated by the arrows directed to the sides of unit OU, forces theair through the outer unit coil by a means of a fan (not shown) andexpels the air as indicated by the arrows above the outdoor unit. Whenoperating as an air conditioner, the air is heated by the condenser coilwithin the outdoor unit and exits the top of the unit at a temperaturehigher than it entered the sides. On the contrary, air is circulatedover the indoor coil IC, and is then circulated through the residence bymeans of duct work D, as indicated by the arrows in FIG. 1. The overallsystem operates to maintain a desired temperature as set by a thermostatT. When the temperature sensed inside the residence is higher than theset point on the thermostat (plus a small amount) the air conditionerwill become operative to refrigerate additional air for circulationthrough the residence. When the temperature reaches the set point (minusa small amount) the unit will stop the refrigeration cycle temporarily.

When the unit in FIG. 1 operates as a heat pump, the roles of the coilsare simply reversed. That is, the coil of the outdoor unit will serve asan evaporator to evaporate refrigerant and thereby cool air entering theoutdoor unit as the air passes over the outdoor unit coil. On thecontrary, the indoor coil IC will receive a stream of air blown over itand will heat the air by condensing a refrigerant.

FIG. 2 illustrates a partially exploded view of one of the units shownin FIG. 1, in this case the outdoor unit OU. In general, the unit may bethought of as including an upper assembly UA made up of a shroud, a fanassembly, a fan drive motor, and so forth. In the illustration of FIG.2, the fan and fan drive motor are not visible because they are hiddenby the surrounding shroud. The outdoor coil OC is housed within thisshroud and is generally disposed to surround or at least partiallysurround other system components, such as a compressor, an expansiondevice, a control circuit, and so forth as described more fully below.

FIG. 3 illustrates another exemplary application for the presentinvention, in this case an HVAC&R system for building environmentalmanagement. In the embodiment, illustrated in FIG. 3, a Building BL iscooled by a system that includes a chiller CH, which is typicallydisposed on or near the building, or in an equipment room or basement.In the embodiment illustrated in FIG. 3, the chiller CH is a roof topair-cooled device that implements a refrigeration cycle to cool water.The water is circulated to a building through water conduits WC. Thewater conduits are routed to air handlers AH at individual floors orsections of the building. The air handlers are also coupled to duct workDU that is adapted to blow air from an outside intake OI.

In operation, the chiller, which includes heat exchangers for bothevaporating and condensing a refrigerant as described above, cools waterthat is circulated to the air handlers. Air blown over additional coilsthat receive the water in the air handlers causes the water to increasein temperature and the circulated air to decrease in temperature. Thecooled air is then routed to various locations in the building viaadditional duct work. Ultimately, distribution of the air is routed todiffusers that deliver the cooled air to offices, apartments, hallways,and any other interior spaces within the building. In many applications,thermostats or other command devices (not shown in FIG. 3) will serve tocontrol the flow of air through and from the individual air handlers andduct work to maintain desired temperatures at various locations in thestructure.

FIG. 4 illustrates a partially exploded view of one of the units asshown in FIG. 3, in this case an HVAC&R system for buildingenvironmental management. In general, the unit may be thought of asincluding an upper assembly UA made up of a shroud, a fan assembly, afan drive motor, and so forth. In the illustration of FIG. 4, the fan isvisible on top of the surrounding shroud. The multichannel coils MC arehoused within this shroud and are generally deposed on top or at leastpartially on top of other system components, such as a compressor, anexpansion device, a control circuit, and so forth as described morefully below. The multichannel coils MC are disposed at an angle toprovide more efficient cooling of the coils and to assist with drainingor liquid buildup from rain and the like.

FIG. 5 illustrates the air conditioning system 10, which usesmultichannel tubes. Refrigerant flows through the system within closedrefrigeration loop 12. The refrigerant may be any fluid that absorbs andextracts heat. For example, the refrigerant may be hydrofluorocarbon(HFC) based R-410A, R-407, or R-134a, or it may be carbon dioxide(R-744a) or ammonia (R-717). The air conditioning system 10 includescontrol devices 14 which enable the system 10 to cool an environment toa prescribed temperature.

The system 10 cools an environment by cycling refrigerant within theclosed refrigeration loop 12 through condenser 16, compressor 18,expansion device 20, and evaporator 22. The refrigerant enters thecondenser 16 as a high pressure and temperature vapor and flows throughthe multichannel tubes of the condenser 16. A fan 24, which is driven bya motor 26, draws air across the multichannel tubes. The fan 24 may pushor pull air across the tubes. Heat transfers from the refrigerant vaporto the air producing heated air 28 while causing the refrigerant vaporto condense into a liquid. The liquid refrigerant then flows into anexpansion device 20 where the refrigerant expands to become a lowpressure and temperature liquid. Typically, the expansion device 20 willbe a thermal expansion valve (TXV); however, in other embodiments, theexpansion device may be an orifice or a capillary tube. As those skilledin the art will appreciate, after the refrigerant exits the expansiondevice, some vapor refrigerant may be present in addition to the liquidrefrigerant.

From the expansion device 20, the refrigerant enters the evaporator 22and flows through the evaporator multichannel tubes. A fan 30, which isdriven by a motor 32, draws air across the multichannel tubes. Heattransfers from the air to the refrigerant liquid producing cooled air 34and causing the refrigerant liquid to boil into a vapor. As will beappreciated by those skilled in the art, the fan may be replaced by apump, which draws fluid across the multichannel tubes.

The refrigerant then flows to compressor 18 as a low pressure andtemperature vapor. The compressor 18 reduces the volume available forthe refrigerant vapor, consequently, increasing the pressure andtemperature of the vapor refrigerant. The compressor may be any suitablecompressor such as a screw compressor, reciprocating compressor, rotarycompressor, swing link compressor, scroll compressor, centrifugalcompressor or turbine compressor. The compressor 18 is driven by a motor36, which receives power from a variable speed drive (VSD) or a directAC or DC power source. In one embodiment, the motor 36 receives fixedline voltage and frequency from an AC power source although in someapplications the motor may be driven by a variable voltage or frequencydrive. The motor may be a switched reluctance (SR) motor, an inductionmotor, an electronically commutated permanent magnet motor (ECM), or anyother suitable motor type. The refrigerant exits the compressor 18 as ahigh temperature and pressure vapor that is ready to enter the condenserand begin the refrigeration cycle again.

The operation of the refrigeration cycle is governed by control devices14 which include control circuitry 38, a thermostat 40, and atemperature sensor 42. The control circuitry 38 is coupled to motors 26,32, 36 which drive the condenser fan 24, the evaporator fan 30, and thecompressor 18, respectively. The control circuitry uses informationreceived from the thermostat 40 and the sensor 42 to determine when tooperate the motors 26, 32, 36 that drive the air conditioning system.For example, in a residential air conditioning system, the thermostat 40may be a programmable 24 volt thermostat that provides a temperature setpoint to the control circuitry 38. The sensor 42 determines the ambientair temperature and provides the temperature to the control circuitry38. The control circuitry 38 then compares the temperature received fromthe sensor to the temperature set point received from the thermostat. Ifthe temperature is higher than the set point, the control circuitry mayturn on the motors 26, 32, 36 to run the air conditioning system 10.Additionally, the control circuitry may execute hardware or softwarecontrol algorithms to regulate the air conditioning system. In someembodiments, the control circuitry 38 may include an analog to digital(A/D) converter, a microprocessor, a non-volatile memory, and aninterface board. Other devices may, of course, be included in thesystem, such as additional pressure and/or temperature transducers orswitches that sense temperatures and pressures of the refrigerant, theheat exchangers, the inlet and outlet air, and so forth.

FIG. 6 illustrates a heat pump system 44 that uses multichannel tubes.Because the heat pump may be used for both heating and cooling,refrigerant flows through a reversible refrigeration/heating loop 46.The refrigerant may be any fluid that absorbs and extracts heat.Additionally, the heating and cooling operations are regulated bycontrol devices 48.

The heat pump system 44 includes an outside coil 50 and an inside coil52 that both operate as heat exchangers. As noted above, the coils mayfunction as either an evaporator or a condenser depending on the heatpump operation mode. For example, when the heat pump system 44 isoperating in cooling (or “AC”) mode, the outside coil 50 functions as acondenser, releasing heat to the outside air, while the inside coil 52functions as an evaporator, absorbing heat from the inside air. On thecontrary, when the heat pump system 44 is operating in heating mode, theoutside coil 50 functions as an evaporator, absorbing heat from theoutside air, while the inside coil 52 functions as a condenser,releasing heat to the inside air. A reversing valve 54 is positioned onthe reversible loop 46 between the coils to control the direction ofrefrigerant flow and thereby to switch the heat pump between heatingmode and cooling mode.

The heat pump system 44 also includes two metering devices 56, 58 fordecreasing the pressure and temperature of the refrigerant before itenters the evaporator. As will be appreciated by those skilled in theart, the metering device also acts to regulate refrigerant flow into theevaporator so that the amount of refrigerant entering the evaporatorequals the amount of refrigerant exiting the evaporator. The meteringdevice used depends on the heat pump operation mode. For example, whenthe heat pump system is operating in cooling mode, refrigerant bypassesmetering device 56 and flows through metering device 58 before enteringthe inside coil 52, which acts as an evaporator. Similarly, when theheat pump system is operating in heating mode, refrigerant bypassesmetering device 58 and flows through metering device 56 before enteringthe outside coil 50, which acts as an evaporator. In other embodiments,a single metering device may be used for both heating mode and coolingmode. The metering devices 56, 58 typically are thermal expansion valves(TXV), but also may be orifices or capillary tubes.

The refrigerant enters the evaporator, which is the outside coil 50 inheating mode and the inside coil 52 in cooling mode, as a lowtemperature and pressure liquid. As will be appreciated by those skilledin the art, some vapor refrigerant may also be present as a result ofthe expansion process that occurs in the metering device 56, 58. Therefrigerant flows through multichannel tubes in the evaporator andabsorbs heat from the air changing the refrigerant into a vapor. Incooling mode, the indoor air passing over the multichannel tubes alsomay be dehumidified. The moisture from the air may condense on the outersurface of the multichannel tubes and consequently be removed from theair.

After exiting the evaporator, the refrigerant passes through thereversing valve 54 and into the compressor 60. The compressor 60decreases the volume of the refrigerant vapor, consequently, increasingthe temperature and pressure of the vapor. Here again, the compressormay be any suitable compressor such as a screw compressor, reciprocatingcompressor, rotary compressor, swing link compressor, scroll compressor,centrifugal compressor or turbine compressor.

From the compressor, the increased temperature and pressure vaporrefrigerant flows into a condenser, the location of which is determinedby the heat pump mode. In cooling mode, the refrigerant flows intooutside coil 50 (acting as a condenser). A fan 62, which is powered by amotor 64, draws air over the multichannel tubes containing refrigerantvapor. As will be appreciated by those skilled in the art, the fan maybe replaced by a pump, which draws fluid across the multichannel tubes.The heat from the refrigerant is transferred to the outside air causingthe refrigerant to condense into a liquid. In heating mode, therefrigerant flows into inside coil 52 (acting a condenser). A fan 66,which is powered by a motor 68, draws air over the multichannel tubescontaining refrigerant vapor. The heat from the refrigerant istransferred to the inside air causing the refrigerant to condense into aliquid.

After exiting the condenser, the refrigerant flows through the meteringdevice (56 in heating mode and 58 in cooling mode) and returns to theevaporator (outside coil 50 in heating mode and inside coil 52 incooling mode) where the process begins again.

In both heating and cooling modes, a motor 70 drives the compressor 60and circulates refrigerant through the reversible refrigeration/heatingloop 46. The motor may receive power either directly from an AC or DCpower source or from a variable speed drive (VSD). As in the previousexample, the motor may be a switched reluctance (SR) motor, an inductionmotor, an electronically commutated permanent magnet motor (ECM), or anyother suitable motor type.

The operation of the motor 70 is controlled by control circuitry 72. Thecontrol circuitry 72 receives information from a thermostat 74 andsensors 76, 78, 80 and uses the information to control the operation ofthe heat pump system 44 in both cooling mode and heating mode. Forexample, in cooling mode, the thermostat provides a temperature setpoint to the control circuitry 72. The sensor 80 measures the ambientindoor air temperature and provides it to the control circuitry 72. Thecontrol circuitry 72 then compares the air temperature to thetemperature set point and engages the compressor motor 70 and fan motors64 and 68 to run the cooling system if the air temperature is above thetemperature set point. Likewise, in heating mode, the control circuitry72 compares the air temperature from the sensor 80 to the temperatureset point from the thermostat 74 and engages the motors 64, 68, 70 torun the heating system if the air temperature is below the temperatureset point.

The control circuitry 72 also uses information received from thethermostat 40 to switch the heat pump system 44 between heating mode andcooling mode. For example, if the thermostat is set to cooling mode, thecontrol circuitry 72 will send a signal to a solenoid 82 to place thereversing valve 54 in the air conditioning position 84. Consequently,the refrigerant will flow through the reversible loop 46 as follows: therefrigerant exits compressor 60, is condensed in outside coil 50, isexpanded by metering device 58, and is evaporated by inside coil 52. Onthe contrary, if the thermostat is set to heating mode, the controlcircuitry 72 will send a signal to solenoid 82 to place the reversingvalve 54 in the heat pump position 86. Consequently, the refrigerantwill flow through the reversible loop 46 as follows: the refrigerantexits compressor 60, is condensed in inside coil 52, is expanded bymetering device 56, and is evaporated by outside coil 50.

The control circuitry 72 may execute hardware or software controlalgorithms to regulate the heat pump system 44. In some embodiments, thecontrol circuitry may include an analog to digital (A/D) converter, amicroprocessor, a non-volatile memory, and an interface board.

The control circuitry also may initiate a defrost cycle when the system44 is operating in heating mode. When the outdoor temperature approachesfreezing, moisture in the outside air that is directed over outside coil50 may condense and freeze on the coil. The sensor 76 measures theoutside air temperature, and the sensor 78 measures the temperature ofthe outside coil 50. These sensors provide the temperature informationto the control circuitry which determines when to initiate a defrostcycle. For example, if either of the sensors 76, 78 provides atemperature below freezing to the control circuitry, the system 44 maybe placed in defrost mode. In defrost mode, the solenoid 82 is actuatedto place the reversing valve 54 to air conditioning position 84, and themotor 64 is shut off to discontinue air flow over the multichannels. Thesystem 44 then operates in cooling mode until the increased temperatureand pressure refrigerant flowing through the outside coil defrosts thecoil 50. Once the sensor 78 detects that the coil 50 is defrosted, thecontrol circuitry 72 returns the reversing valve 54 to heat pumpposition 86. As will be appreciated by those skilled in the art, thedefrost cycle can be set to occur at many different time and temperaturecombinations.

FIG. 7 is a perspective view of an exemplary heat exchanger, which maybe used in an air conditioning system 10 or a heat pump system 44. Theexemplary heat exchanger may be a condenser 16, an evaporator 22, anoutside coil 50, or an inside coil 52, as shown in FIGS. 5 and 6. Itshould also be noted that in similar or other systems, the heatexchanger may be used as part of a chiller or in any other heatexchanging application. The heat exchanger includes manifolds 88, 90that are connected by multichannel tubes 92. Although 30 tubes are shownin FIG. 7, the number of tubes may vary. The manifolds and tubes may beconstructed of aluminum or any other material that promotes good heattransfer. Refrigerant flows from the manifold 88 through first tubes 94to the manifold 90. The refrigerant then returns to the manifold 88through second tubes 96. In some embodiments, the heat exchanger may berotated approximately 90 degrees so that the multichannel tubes runvertically between a top manifold and a bottom manifold. Additionally,the heat exchanger may be inclined at an angle relative to the vertical.Furthermore, although the multichannel tubes are depicted as having anoblong shape, the tubes may be any shape, such as tubes with across-section in the form of a rectangle, square, circle, oval, ellipse,triangle, trapezoid, or parallelogram. In some embodiments, the tubesmay have a diameter ranging from 0.5 mm to 3 mm. It should also be notedthat the heat exchanger may be provided in a single plane or slab, ormay include bends, corners, contours and so forth.

In some embodiments, the construction of the first tubes 94 may differfrom the construction of the second tubes 96. Tubes may also differwithin each section. For example, the tubes may all have identical crosssections, or the tubes in the first section may be rectangular while thetubes in the second section are oval. The internal construction of thetubes, as described below with regard to FIG. 8 may also vary within andacross tube sections.

Returning to FIG. 7, refrigerant enters the heat exchanger through aninlet 98 and exits the heat exchanger through an outlet 100. AlthoughFIG. 7 depicts the inlet at the top of the manifold 88 and the outlet atthe bottom of the manifold, the inlet and outlet positions may beinterchanged so that fluid enters at the bottom and exits at the top.The fluid may also enter and exit the manifold from multiple inlets andoutlets positioned on bottom, side, or top surfaces of the manifold.Baffles 102 separate the inlet 98 and outlet 100 portions of themanifold 88. Although a double baffle 102 is illustrated, any number ofone or more baffles may be employed to create separation of the inlet 98and the outlet 100.

Fins 104 are located between the multichannel tubes 92 to promote thetransfer of heat between the tubes 92 and the environment. In oneembodiment, the fins are constructed of aluminum, brazed or otherwisejoined to the tubes, and disposed generally perpendicular to the flow ofrefrigerant. However, in other embodiments the fins may be made of othermaterials that facilitate heat transfer and may extend parallel or atvarying angles with respect to the flow of the refrigerant.Additionally, the fins may be louvered fins, corrugated fins, or anyother suitable type of fin.

As noted above, in a typical evaporator heat exchanger application, themajority of the heat transfer occurs due to a phase change of therefrigerant. Refrigerant exits the expansion device as a low pressureand temperature liquid and enters the evaporator. As the liquid travelsthrough the first multichannel tubes 94, the liquid absorbs heat fromthe outside environment causing the liquid to warm from its subcooledtemperature (i.e., a number of degrees below the boiling point). Then,as the liquid refrigerant travels through the second multichannel tubes96, the liquid absorbs more heat from the outside environment causing itto boil into a vapor. Although evaporator applications typically useliquid refrigerant to absorb heat, some vapor may be present along withthe liquid due to the expansion process. The amount of vapor may varybased on the type of refrigerant used. In some embodiments, therefrigerant may contain approximately 15% vapor by weight and 90% vaporby volume. This vapor has a lower density than the liquid, causing thevapor to separate from the liquid within the manifold 88. Consequently,certain flow channels of tubes 92 may contain only vapor.

FIG. 8 shows a perspective view of a tube 92 shown in FIG. 7.Refrigerant flows through flow channels 106 contained within the tubes94. The flow channels 106 may be parallel to one another. The directionof fluid flow 108 is from manifold 88 shown in FIG. 7 to manifold 90shown in FIG. 7 within the first tubes. The direction of fluid flow isreversed within the second tubes. Because the refrigerant withinmanifold 88 is a mixture of liquid phase and vapor phase refrigerant,the flow channels 106 may contain some liquid and some vapor.Additionally, because of the density difference, which causes separationof phases, some flow channels within the channel section 110 may containonly vapor phase refrigerant while other flow channels may contain onlyliquid phase refrigerant. The flow channels containing only vapor phaserefrigerant are not able to absorb as much heat because the refrigeranthas already changed phases. The fluid in the flow channels may berefrigerant, brine, or other fluid capable of the necessary phasechange.

After flowing through the channel section 110, the refrigerant reachesthe open section 112. In the open section, the interior walls that formthe flow channels have been removed or interrupted. Consequently, theopen section includes an open channel 114 spanning the width W of thetube 92 where mixing of the two phases of refrigerant can occur. Mixedflow 118 occurs within this section causing the fluid flow 108 from theflow channels 106 to cross paths and mix. Thus, flow channels containingall (or primarily) vapor phase may mix with flow channels containing all(or primarily) liquid phase, providing a more homogenous distribution ofrefrigerant. Additionally, flow channels containing differentpercentages of vapor and liquid may also mix.

From the open section 112, the refrigerant enters flow channels 120contained within channel section 122. The fluid flow 124 through thesechannels may contain a more even distribution of vapor and liquid phasesdue to the mixed flow 118 that occurred within the open channel 114. Thetube 92 may contain any number of open sections 112 where mixing mayoccur. Thus, rather than allowing vapor alone to be channeled throughcertain flow paths, the internal wall interruptions permit mixing of thephases, allowing increased phase change to occur in all of the flowpaths (through which an increasingly mixed phase flow will bechanneled). The internal wall interruptions also allow the tubes to besegregated into sections for repair purposes. For example, if a flowchannel contained within channel section 110 becomes blocked, plugged,or requires repair, that section of the flow channel may be removed fromservice or bypassed while the corresponding flow channel within channelsection 122 continues to receive refrigerant flow.

In the arrangement shown in FIG. 9, the outer coils, 200, 210 can have amuch higher air flow than the interior coils 202, 204, 206, 208 becauseof the placement on the outside of the system. Higher air flow through acoil provides better coil performance, resulting in lower refrigerantliquid temperatures within the flow channels. The lower the refrigerantliquid temperatures, the more efficient the system is during the coolingmode of operation. Air flow rates through the outer coils 200, 210 canbe almost twice as high as that through the inside coils 202, 204, 206,208. Table 1, below, provides sample refrigerant temperatures at theexit of each coil in a conventional condenser. The temperatures of eachcoil vary greatly, which results in an inefficient chiller system.

TABLE 1 Coil number 200 202 204 206 208 210 Sample Temp. 96.7 109.4103.3 106.3 113.6 102.6 (Degrees Fahrenheit)

To regulate the flow of refrigerant in the coils a valve or orifice 220may be disposed in the outlet 100 of at least one of the coils. Thevalve or orifice 220 provides the necessary refrigerant flow for eachindividual coil, depending on the amount of air flow the coil receives.The refrigerant is regulated to allow the air flow to cool therefrigerant in the flow channel and provide a more efficient chiller.FIG. 10 illustrates a valve or orifice 220 as disposed in the outlet 100of at least one of the coils. The valve or orifice 220 restricts therefrigerant flow in the flow channel, and provide a control of therefrigerant flow. The restriction of the refrigerant flow allows the airto cool the refrigerant better, thereby providing a lower liquidtemperature in the coils. The valve or orifice 220 may also allow morerefrigerant flow, thereby providing a pressure drop in the correspondingliquid line of the coil and allowing more refrigerant to flow. In otherembodiments, a reduced line size, e.g., venturi, or otherflow-restricting component may be interchanged with the valve or orifice220. The sizing or positioning of the valve or orifice 220 is adjustableto obtain the desired pressure drop or the desired refrigerant liquidtemperature exiting that particular coil. The valve or orifice 220 maybe controlled by an automatic control, using circuitry ormicroprocessors. Another embodiment includes the valve or orifice 220being controlled manually according to the amount of air flow throughoutthe condenser.

In one embodiment, one or more valves or orifices 220 may beincorporated in coils 200, 202, 204, 206, 208, and 210 as a unitary partof the coil. Table 2, below, provides sample refrigerant temperatures atthe exit of each coil in which coils 202 and 208 include a valve ororifice 220 in the discharge connection. The temperatures of the coilsare now closer in range, resulting in a more efficient chiller system.

TABLE 2 Coil number 200 202 204 206 208 210 Sample Temp. 98.7 101.3103.5 103.4 102.8 101.3 (Degrees Fahrenheit)

The incorporation of one or more valves or orifices 220 with thedischarge connections of the coils can substantially lower refrigerantliquid temperature entering the expansion valve by approximately 1.5deg. Fahrenheit with no change in condensing temperature. The resultinglower liquid temperature gives an approximate substantially 1% increasein both chiller capacity and efficiency. In addition, the lower liquidtemperature substantially eliminates vapor from exiting some of thecoils. This is important because refrigerated vapor can createoperational problems with expansion valves. Lastly, the incorporation ofone or more orifices with the discharge connections of the coils may beincorporated with multichannel and conventional channel applicationswith uneven air distribution. It should be noted that while referencehas been made to air flow cooling the fluid in the flow tubes 106, anytype of non volatile fluid may be used, e.g. water. The examplesprovided above in Table 1 and Table 2 include condensers with sixmicrochannel coils, however, one of ordinary skill in the art wouldappreciate that any number of coils may be used for the microchannel inthe condenser.

It is understood that the present discussion describes the use of theinvention in condensers with multiple microchannel coils. The inventionmay also be used with other types of condenser applications. Thesecondenser applications include, but are not limited to, conventionalround-tube coils, water-cooled condensers, individual tubes withincondensers or any condenser with tube-side condensation, flowdistribution issues, or other problems or issues that create animbalance in condenser performance.

It is also understood that while the orifice or valve is described asbeing disposed in the outlet or near the exit of the condenser, theorifice or valve may be placed in liquid headers, at an the outletindividual tubes, in coils with reduced air flow, in coils with higherair temperatures, or in coils with reduced heat transfer. Likewise, theorifice or valve may be applied to water-cooled condensers withtube-side condensation or sections of the condenser with reduced heattransfer or reduced water flow. The invention may also apply to anyapplication with issues or problems with condenser performance.

It should be noted that the present discussion makes use of the term“multichannel” tubes or “multichannel heat exchanger” to refer toarrangements in which heat transfer tubes include a plurality of flowpaths between manifolds that distribute flow to and collect flow fromthe tubes. A number of other terms may be used in the art for similararrangements. Such alternative terms might include “microchannel”(sometimes intended to imply having fluid passages on the order of amicrometer and less), and “microport”. Other terms sometimes used in theart include “parallel flow” and “brazed aluminum”. However, all sucharrangements and structures are intended to be included within the scopeof the term “multichannel”. In general, such “multichannel” tubes willinclude flow paths disposed along the width or in a plane of a generallyflat, planar tube, although, again, the invention is not intended to belimited to any particular geometry unless otherwise specified in theappended claims.

It should also be noted that while the present discussion refers to thecondenser as being a part of a multichannel heat exchanger or an HVAC&Rsystem, the condenser could be used in any suitable application, such asa chemical process. Further, one of ordinary skill in the art wouldappreciate that while the term refrigerant is used as the fluid in thecoils, any suitable fluid may be used, such as, but not limited to,propane or chlorine. The fluid used on the outside of the tubes may beany suitable liquid or gas such as, but not limited to air, water orbrine.

It should also be understood that the application is not limited to thedetails or methodology set forth in the following description orillustrated in the figures. It should also be understood that thephraseology and terminology employed herein is for the purpose ofdescription only and should not be regarded as limiting.

While the exemplary embodiments illustrated in the figures and describedherein are presently preferred, it should be understood that theseembodiments are offered by way of example only. Accordingly, the presentapplication is not limited to a particular embodiment, but extends tovarious modifications that nevertheless fall within the scope of theappended claims. The order or sequence of any processes or method stepsmay be varied or re-sequenced according to alternative embodiments.

It is important to note that the construction and arrangement of themultichannel coil as shown in the various exemplary embodiments isillustrative only. Although only a few embodiments have been describedin detail in this disclosure, those skilled in the art who review thisdisclosure will readily appreciate that many modifications are possible(e.g., variations in sizes, dimensions, structures, shapes andproportions of the various elements, values of parameters, mountingarrangements, use of materials, colors, orientations, etc.) withoutmaterially departing from the novel teachings and advantages of thesubject matter recited in the claims. For example, elements shown asintegrally formed may be constructed of multiple parts or elements, theposition of elements may be reversed or otherwise varied, and the natureor number of discrete elements or positions may be altered or varied.Accordingly, all such modifications are intended to be included withinthe scope of the present application. The order or sequence of anyprocess or method steps may be varied or re-sequenced according toalternative embodiments. In the claims, any means-plus-function clauseis intended to cover the structures described herein as performing therecited function and not only structural equivalents but also equivalentstructures. Other substitutions, modifications, changes and omissionsmay be made in the design, operating conditions and arrangement of theexemplary embodiments without departing from the scope of the presentapplication.

1. An HVAC&R system comprising: a compressor, a condenser, anevaporator, and an expansion valve connected in a closed refrigerantloop; the condenser further comprising: at least two fluid flow pathsbeing cooled by air flow forced through the condenser by at least onecondenser fan, the at least two fluid flow paths each having an inletand an outlet and a fluid flow between the inlet and the outlet, and theat least two fluid flow paths having an air flow for cooling the fluidin the at least two fluid flow paths, the air flow being variable acrossthe condenser; at least one flow regulator being disposed in at leastone outlet to regulate at least one fluid flow in response to thevariable air flow and to regulate the fluid flow in the at least twoflow paths to achieve a substantially equal fluid temperature.
 2. TheHVAC&R system of claim 1 wherein the fluid regulator is an orifice. 3.The HVAC&R system of claim 1 wherein the fluid regulator is a valve. 4.The HVAC&R system of claim 1 wherein the condenser comprises amultichannel heat exchanger.
 5. The HVAC&R system of claim 4 wherein themultichannel heat exchanger has six coils.
 6. The HVAC&R system of claim5 wherein a flow regulator is disposed in the outlet of two of the sixcoils.
 7. The HVAC&R system of claim 1 wherein the flow regulator is aunitary piece of outlet.
 8. The HVAC&R system of claim 1 wherein thefluid is refrigerant.
 9. A condenser comprising: at least two fluid flowpaths being cooled by air flow drawn through the condenser by at leastone condenser fan, the at least two fluid flow paths having an inlet andan outlet and a fluid flow between the inlet and the outlet, and the atleast two fluid flow paths having an air flow for cooling the fluid inthe at least two fluid flow paths, the air flow being variable acrossthe condenser; at least one flow regulator being disposed in at leastone outlet to regulate at least one fluid flow in response to thevariable air flow and to regulate the fluid flow in the at least twoflow paths to achieve a substantially equal fluid temperature.
 10. Thecondenser of claim 9 wherein the fluid regulator is an orifice.
 11. Thecondenser of claim 9 wherein the fluid regulator is a valve.
 12. Thecondenser of claim 9 wherein the condenser comprises a multichannel heatexchanger.
 13. The condenser of claim 12 wherein the multichannel heatexchanger has six coils.
 14. The condenser of claim 13 wherein a flowregulator is disposed in the outlet of two of the six coils.
 15. Thecondenser of claim 12 wherein the flow regulator is a unitary piece ofoutlet.
 16. The condenser of claim 12 wherein the fluid is refrigerant.17. A condenser comprising: a multichannel heat exchanger; at least twofluid flow paths in the multichannel heat exchanger being cooled by airflow drawn through the condenser by at least one condenser fan, the atleast two fluid flow paths having an inlet and an outlet and a fluidflow between the inlet and the outlet, and the at least two fluid flowpaths having an air flow for cooling the fluid in the at least two fluidflow paths, the air flow being variable across the condenser; at leastone flow regulator being disposed in at least one outlet to regulate atleast one fluid flow in response to the variable air flow and toregulate the fluid flow in the at least two flow paths to achieve asubstantially equal fluid temperature.
 18. The condenser of claim 17wherein the fluid regulator is an orifice.
 19. The condenser of claim 17wherein the fluid regulator is a valve.